The Icelandic word for "rain" and the Old English for "aurochs" go back to two different Proto-Germanic words, *ūruz and *ūrą (although possibly from the same root[original research?]). The Norwegian meaning "dross, slag" is more obscure, but may be an Iron Age technical term derived from the word for water (cf. the Kalevala, where iron is compared to milk).
Because of this, it is difficult to reconstruct a Proto-Germanic name for the Elder Futhark rune. It may have been *ūruz "aurochs" (see also Bull worship), or *ūrą "water". The aurochs is preferred by authors of modern runic divination systems, but both seem possible, compared to the names of the other runes: "water" would be comparable to "hail" and "lake", and "aurochs" to "horse" or "elk" (although the latter name is itself uncertain). The Gothic alphabet seems to support "aurochs", though: as the name of the letter 𐌿 u is urus.
Rune poems
It is recorded in all three rune poems, and it is called Ur in all, however with different meanings:
Old Norwegian ᚢ Úr er af illu jarne;
opt løypr ræinn á hjarne.
Dross comes from bad iron;
the reindeer often races over the frozen snow.
Old Icelandic ᚢ Úr er skýja grátr
ok skára þverrir
ok hirðis hatr.
umbre vísi
Rain is lamentation of the clouds
and ruin of the hay-harvest
and abomination of the shepherd.
Old English ᚢ Ur bẏþ anmod ond oferhẏrned,
felafrecne deor, feohteþ mid hornum
mære morstapa; þæt is modig ƿuht.
The aurochs is proud and has great horns;
it is a very savage beast and fights with its horns;
a great ranger of the moors, it is a creature of mettle.
References
^Page, R.I. (2005). Runes, page 15. The British Museum Press ISBN0-7141-8065-3
